Some mechanical systems require that one or more functional elements be physically moved along a travel direction. In one common approach, the functional elements are mounted on a carriage that is driven by a motor. To convert the rotary output of the motor to the linear motion required for the functional elements, a leadscrew is driven by a rotary-output motor, a follower on the carriage engages the threads on the leadscrew, and the carriage and functional elements move linearly as the motor shaft turns.
Leadscrew and other drives are widely and successfully used for many applications. In others, however, they have shortcomings. One is that the positioning of the functional element is not always precisely repeatable. That is, the position of the follower and the functional element may be infinitely varied, so that the position of the functional element may be slightly different with each repositioning. Another problem is that, when the mechanical system is mechanically shocked or severely shaken, the position of the functional element may be disturbed from its desired position. The feedback controller of the leadscrew mechanical drive may be able to compensate for this undesired movement. If the drive motor and/or the feedback controller are not operable, as for example when they are intentionally or unintentionally shut down, there is no capability for compensation, and the disturbance to the position of the functional element is not corrected. Yet another shortcoming in some applications is that the physical envelope of the leadscrew drive system is elongated to allow for the in-line coupling of the motor and the leadscrew. This elongated physical envelope may be unacceptable for some applications. It is difficult to miniaturize the leadscrew mechanical drive system in some instances. Yet another shortcoming is that the alignment of leadscrew mechanical drives is difficult to establish initially and to maintain throughout the service life, particularly where the required range of travel of the functional elements is large and therefore the leadscrew is long.
There is a need for a mechanical drive system that overcomes these shortcomings. The present invention fulfills this need, and further provides related advantages.